对数变换

//取对数
void CMyDIPView::OnMenuitem32778()
{
 // TODO: Add your command handler code here
 int i,j;
 double c;
    unsigned char *lpSrc;
 CMyDIPDoc* pDoc = GetDocument();
 ASSERT_VALID(pDoc);
 if(pDoc->m_hDIB == NULL)
  return ;
 LPSTR lpDIB = (LPSTR) ::GlobalLock((HGLOBAL) pDoc->m_hDIB);
 LPSTR lpDIBBits=::FindDIBBits (lpDIB);
 int cxDIB = (int) ::DIBWidth(lpDIB);         // Size of DIB - x
 int cyDIB = (int) ::DIBHeight(lpDIB);        // Size of DIB - y
 long lLineBytes = WIDTHBYTES(cxDIB * 8);     // 计算图像每行的字节数
 // 每行
 for(i = 0; i < cyDIB; i++)
 {
  // 每列
  for(j = 0; j < cxDIB; j++)
  {
   // 指向DIB第i行，第j个象素的指针
   lpSrc = (unsigned char*)lpDIBBits + lLineBytes * (cyDIB - 1 - i) + j;
   
   // 计算新的灰度值
   c=255/log(256);
   *(lpSrc) = BYTE(c*log(*lpSrc+1));
  }
 }
 ::GlobalUnlock((HGLOBAL) pDoc->m_hDIB);
    Invalidate(TRUE);
}